Ph Drops when pump is on low speed, why? (Hayward pro-logic, 13,000gal SWpool w/chlorine generator)

~STOLEN~

Member
Jul 11, 2019
19
Indianapolis, IN
The system is a hayward pro-logic which has chlorine generator, heater and acid dispenser, and the salt in the pool is @ 3800ppm currently, the system is set to keep chlorine at 725 which it does perfectly.

We have a 2 speed Hayward pump that is recommended to be on high speed for a min. of 8 hrs. That being said, I was told by other members that my pump is running too much, so i tried to dial the run time down and the Ph plummets to around 5.7 which isn't acceptable.
The problem is that the Acid dispenser times out after 120min of inactivity. So if i'm not around to check the panel (cause i'm at work all day) there is no way for me to reset the default timeout (start it over) function AND the pump is on low speed, i get home to very low Ph levels. AND the acid is set by hayward to only work on HIGH speed

Does anyone have a similar problem?

I did pick up some soda ash this weekend but still havent added it. I'm just not sure whether running the pump LONGER is the best idea since no one is in it from Mon-Thur
 

Jimrahbe

Mod Squad
TFP Expert
LifeTime Supporter
Jul 7, 2014
13,653
Bedford, TX
S,,

I'm sure what you say is happening, but what you are saying makes no sense... If the Acid dispenser is not working when on low speed, then your pH should be stable or increasing.. If the pH drops on low, it seems to me the problem is that you are getting too much acid when on low speed.

That said, not many of us here at TFP, are fans of automated dosing systems.. While they sound good in theory, they tend to degrade over time and become more of a headache than a benefit.

Hayward, or Pentair in my case, does not tell me what speeds I have to run.. If they did, I'd have a few suggestions for them.. :mrgreen:

If you are going to ask us for chemical advice, we will need a set of test data as follows..

FC
CC
pH
TA
CH
CYA
Salt


Thanks,

Jim R.
 

JamesW

TFP Expert
Mar 2, 2011
15,648
Is the feeder pumping acid and lowering the pH or is the reading changing with no acid being pumped?

Is the feeder timing out due to inactivity or from activity?

It doesn't make sense to time out from inactivity.
 

~STOLEN~

Member
Jul 11, 2019
19
Indianapolis, IN
yes the feeder is a pumping a diluted acid mix

The acid doesn't pump on low speed pump setting(hayward's default), so yes inactivity is why its timing out
i just cant figure out why it drops so fast when the only thing that changes is the pump speed

on a side note, this pool is only open to elements from around 4:30pm-10pm at night, all other times the auto-cover is closed
I'll take a pic of the display as soon as i get home

thanks!
 

JamesW

TFP Expert
Mar 2, 2011
15,648
If the feeder does not pump on low, how is the pH dropping?

The inactivity timeout doesn't make sense. You're saying that if it's not pumping acid, it times out?

So, if the pH is stable for a few days, the pump times out?

How does that make sense?
 

JamesW

TFP Expert
Mar 2, 2011
15,648
So, the question is whether the actual pH in the pool is dropping or the reading becomes inaccurate.

I suspect that the sensor has an error at low flow probably due to lack of flow in the test apparatus.

Have you independently tested the pH and TA?

If yes, when was the most recent test and what were the numbers?

If you switch the pump back to high speed, does the pH readout increase?

How old is the system and did it ever work correctly?
 

Jimrahbe

Mod Squad
TFP Expert
LifeTime Supporter
Jul 7, 2014
13,653
Bedford, TX
I agree with you James.. it has to be a sensor error as it makes no sense otherwise..

Thanks,

Jim R.
 

mguzzy

Well-known member
Jul 8, 2015
492
OV, CA
Is it possible to disconnect the dispensing tube an put it in another receptacle to see if it is leaking? AND/OR monitor the Acid in the pool with the Acid dispenser disabled. I am not familiar with how auto dispenser work in pool equipment, but I am familiar with the lab versions.
 

~STOLEN~

Member
Jul 11, 2019
19
Indianapolis, IN
I will do fresh measurements once home from work, recalibrate the

The system was installed in March 8th of this year.
The ph timeout settings are only 60/90/120min

I did an independent test 2 weeks ago when i shut everything down and cleaned the filter cartridges, the sensors and fired it back up. The ph sensor was .1 off the actual reading of my manual test.

I orig came here because i am interested in a chiller for the pool because im seeing temps in the 93-96deg range by 5pm at night and cant use the pool because its too Dang warm. When i posted my run times for my filter and settings, a couple other members suggested that i didnt need to run my pump on high speed for more than a couple hours. SO , i thought maybe that would also lower the temps of the water another degree or 2 and it DID, but then i started seeing the pH going crazy.

im reading and researching as much as possible before asking, but i am fairly new to this so bare with me.
i do appreciate all the help !!
thanks guys!!
 

~STOLEN~

Member
Jul 11, 2019
19
Indianapolis, IN
Here is a pic about the feeder timing out
when i got home the pH was 7.5 (but pump ran on high speed from 8am until 3:30)
pump ran on high speed so the feeder kept the pH where it should have been until it times out for because of being on low speed. By the time i went to bed at 10pm, it was already down to 6.8 pH, when i woke up it was all the way down to 4.9, PUMP still on low speed.
Instead of a timeout error, i got a pH low error, check feeder (as if it ran empty on acid mix)

these are the test results of water as of 7:30am today

Fcl-10
Air-0
Ph-4.9
Cya-0
Salt-3900 ppm
Orp -745
Chlorene Cell type 15

my test doest have TA or CC apparently, can you guys give me info on the one you recommend to help dial this in


thanks again.
 

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JamesW

TFP Expert
Mar 2, 2011
15,648
Does the pH go back to normal when you switch the pump back to high speed?

Do you have a picture of the system?

I think the problem is a sensor error.
 

~STOLEN~

Member
Jul 11, 2019
19
Indianapolis, IN
Yes for the most part, it used to be set to 12hr high speed, 12hrs low speed and ph was normal, and only timed out during the high speed because ph doesnt seem to drop when there is a lot of water movement.

i just looked back in my camera roll, and only pics i have are of during the construction process. ill take a pic of the current setup tonight for ya.
 
Last edited:

JamesW

TFP Expert
Mar 2, 2011
15,648
I recommend that you get a good test kit and maintain the pool without the orp and pH automation.

 

~STOLEN~

Member
Jul 11, 2019
19
Indianapolis, IN
I recommend that you get a good test kit and maintain the pool without the orp and pH automation.


That's disappointing considering the money we just paid for it LOL
ill pick up one of those test kits in the meantime though, thanks!!!
 

Jimrahbe

Mod Squad
TFP Expert
LifeTime Supporter
Jul 7, 2014
13,653
Bedford, TX
S,

I agree with James, but even if you don't want to abandon your system, you need to be able to independently double check what your system is telling you. You just can't assume what the system is telling you is true.. You have to routinely test your pool water and compare it with what the system says. As long as they agree, then everything is good to go. But when things don't agree, you will have to get your system back on track, because the test kit won't lie to you.

Thanks,

Jim R.
 
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mguzzy

Well-known member
Jul 8, 2015
492
OV, CA
Didn't you say this system was installed in March? seems like there might be some warranty coverage. My suggestion to disconnect it was to troubleshoot the device. And maintain it with a test kit for awhile for comparison. It doesn't seem like you are trying to run it in any fashion out of the norm. I've never heard of a dispensing device that keeps dispensing when it fails or faults.. they usually stop. And if your ph is dropping into the 4s it must be going through acid like crazy.

Also you said the dispenser is supposed to be run only when the pump is at full speed. Do you have it on a timer of sorts so the dispenser is only active when the pump is in its high speed cycle?
 
Last edited:

Jimrahbe

Mod Squad
TFP Expert
LifeTime Supporter
Jul 7, 2014
13,653
Bedford, TX
Mguzzy,

The OP's pH is not actually dropping into the 4's.. the system is just reporting it is in the 4's.. A typical problem with automated dosing systems..

Jim R.
 

JamesW

TFP Expert
Mar 2, 2011
15,648
It's important to differentiate between the actual pH and the pH readout on the display.

They should match, but they are two different things.

I think that the actual pH is probably fine.

I think that the problem is a sensor error at low flow causing the readout to be incorrect.